vb.net sql last inserted ID

Question

i'm using VB.NET with an Access Database, I insert values but then I need to get the last inserted ID (auto number) and insert that into a related table.

I have tried @@IDENTITY and MAX(column) but @@IDENTITY returns zero and MAX isn't very dependable (sometimes slow to insert data, so get the ID before the inserted one).

Dim insertSql = datalayer.getDataTable((String.Format("INSERT INTO users (username) VALUES ({0})", username)))

Dim newID = datalayer.getDataTable((String.Format("SELECT @@IDENTITY FROM users")))


Dim con As OleDbConnection = getConnection()
con.Open()
Dim sqlCommand As OleDbCommand = New OleDbCommand(String.Format(insertSql), con)
sqlCommand.ExecuteNonQuery()

This is done in two functions so the above code might look confusing, but thats just taken from the two functions. The two statements are executed, but I have just shown one being executed as an example.

Is there and alternative to @@IDENTITY and MAX, as I carn't seem to see how am going wrong with @@IDENTITY?

Thanks for any advice :).

Answer 1

Its is absolutely crucial than SELECT @@IDENTITY is executed on the same connection (and transaction) than the insert. If your getDataTable() method creates a new connection for each call, then that is why its not working.

Update

Another approach which is preferable is to execute the two statements in one

sql = "INSERT INTO...;SELECT @@IDENTITY..." 
Dim id = sqlCommand.ExecuteScalar(sql)

Update again

It seems like you can't execute multiple functions like this against a MS Access database, Running multiple SQL statements in the one operation.